Ghosts I–IV is the sixth studio album by American industrial rock band Nine Inch Nails, released on March 2, 2008. The team behind the project included Nine Inch Nails front man Trent Reznor, studio-collaborators Atticus Ross and Alan Moulder, and instrumental contributions from Alessandro Cortini, Adrian Belew, and Brian Viglione. Reznor described the music of Ghosts as "a soundtrack for daydreams", a sentiment echoed by many critics who compared it with the work of Brian Eno and Robert Fripp. The songs are unnamed, and are identified only by their track listing and group number.